Process for the separation of seeds by froth flotation



Patented Apr. is, 1939 UNITED STATES mo'cnss ron run snrmanon or snaps BY mom :rsrr N FLO Theodore Earle, Pacific Palisades, Calif.

No Drawing.

Application October 15, 1986, Serial No. 105,632

1': Claim (i. roe-'10s) i This invention relates to a process or method for the separation and classification of seeds,

and-more particularly to a process or method for the application of froth flotation for the successful separation and classification of plant and grass seeds, and has as an object to provide an improved process whereby mixed seeds of different kinds may be separated and classified according to their respective natures, and wherel by seeds of a given variety may be separated and classified according to their relative fertility and potential strength.

A further object of the invention is to provide an improved process susceptible of ready, convenient and inexpensive practice to separate and classify plant seeds according to the variety of seed or according to the relative fertility and strength of seeds in a given variety, or both.

A further object of the invention is to provide v an improved process whereby the principles of froth flotation may be practically and successfully applied to the separation and classification of plant seeds, either for isolation of a given variety of seed from a mixture of diflerent varieties or for-the selection of the relatively stronger and more fertile seeds within a given variety.

It has long been recognized that the various minerals and combinations of minerals present distinct characteristics which may be utilized l, to effect their separation through the process which has come to be known as froth flotation. I have found that difi'erent varieties of plant and grass seeds, and seeds of difierent fertility within a given variety of seed, have different and v definite adsorbtive and other characteristics,

rendering the principle of froth flotation avail-i able for their practical classification and selective separation. However, in carrying out such process certain problems are met which do not arise in minerals separation. Thus certain features must be borne in mind and the reagent to be employed must be selected accordingly, e. g., as to whether the seed is to beused asa food; the edect of the reagent on the sprouting or growing qualities on the seed, whether the seed is to be ediately planted, the presence or absence of the natural husk or hull covering the seed, the character of the soil or climate obtaining during the growth vof the seed insofar as the same may afiect the characteristics thereof in the application of the process, and the bulk, mass and density of the seed under treatment and the strength of'the' froth bubbles necessary to effect separation thereof.

Froth flotation as used in the improved proc ess and as referred to herein is that conventional and well-understood method which involves re- I peated and continued agitation of the material to be separated or classified within, and through a body of liquid to which suitable reagents, have 5 been introduced in one manner or another for the production of a ,froth bed which forms on and is supported above the liquid body. There are several standard types of froth flotation apparatus which may be employed in the adaptation of froth flotation to the separation and classification of plant seeds, but it is to be noted that the froth flotation employed in the improved process difiers materially from float and sink methods and from separatory methods'utilizing surface tension of aliquid, in that the froth fiota-- tion technqiue includes continued agitation of the liquid body and recirculation of the material under treatment throughsaid liquid body to elimi nation of the concentrates from the liquid body and into the froth bed wherewith said concentrates are removed from the flotation appara-' tus.

For the treatment of certain of the smaller seeds afroth flotation machine of standard impeller type will prove reasonably satisfactory, but the larger seeds'are subject to damage thereby;

thus, in generaLthe flotation machine designed for agitation by means of compressed airvorgas is thereforepreferred. The latter type of mao chine may. be ed by the addition of a specially designed impeller, designed to minimize the possibility of damage to the seed, in which v case the impeller acts to difiuse and spread the air or gas stream throughout the liquid body.

In dete the principles involved, a great deal of experimental work was done, with many types arfd'varieties of plant seed, and in every instance some degree of effective separation was obtained, such separations being followed by 40 planting under identical conditions and compari- 1 son ofgrowing eapacities- Itwas found that in some cases the more fertile seed will separate out as a froth concentrate, but in other cases the reverse is true Whilethereis an obvious difference in those portions of a given variety of seed separated by the improved method it can not be said that the better will always appear as concentrates in the flotation cell; since for each variety of seed separation germination and rate of growth twtsmust be completed to determine the relative strength ofthe tails and concentrates resulting when that'particular'sed and efficient. In some cases it may be desirable to condition the seed with certain reagents prior to its treatment in the froth flotation machine and in other instances same may be unnecessary; the desirability of such conditioning is readily determinable by test in the case of any given variety or combination.

In a practical application of the improved process, the first step may involve proper preliminary treatment in cases where desirable. In certain cases, a thorough water-wetting of all of the seed surfaces is necessary to modify and adapt the surface characteristics of the seed for the desired reaction with the reagent before its addition to and agitation with the seed. In any event, it is highly important that the seed tobe separated should be completely immersed in water at some time during the flotation treatmerit.-

The next or coincident phase of the improved process comprises agitation of the seed in a froth rough, dull, etc., each of which characteristics is productive of a definite flotation effect with a given reagent. 4

The difference in the surface characteristics of the seeds will require variation and specific adaptation of the reagents employed and the method utilized in feeding the seeds to the flotation machine. In general, seeds in classes (1) and (2) exhibit a preference for frothing reagents, while those in class (3) react flotatively with certain of the fatty acids and their derivatives; but similar seed varieties in either class (1), (2) or (3) may well exhibit differing preferences for reagents or may react differently in point of time to the same reagent. Frothing reagents, including pine oil, terpineol, cresylic acid, the lower and high alcohols, tar oil, "Airflot, and in general any reagents which are capable'of sufficiently lowering the surface tension of the water, when added in small amounts, were employed, alone and in various combinations with vegetable oils and highly refined mineral oils; oleic acid and other fatty acids and their derivatives were employed for collecting purposes. Certain seeds carry enough naturalfrother to eliminate addition of a froth reagent. The amount of reagent required willvary between a top limit of forty pounds of any one reagent per ton of seed and a. lower limit amounting to only a fraction of one per cent by weight of seed.

Better results may be had in some instances by feeding the seed into the machine and into the liquid below the froth bed and in other instances by'feeding the seed through the froth bed and thence into the liquid. This arises from the fact that where frothers or other relatively insoluble or slightly water soluble reagents are employed, such reagents tend to concentrate on the liquid surface immediately below the froth bed; in such case, seed introduced below the froth line will require longer agitation, and the softening effect of the liquid on the seed covering may vary the normal flotative characteristic. For example: If alfalfa seed be introduced through a froth formed by a reagent of the type of Du Pont frother B23 all of the pure and fertile seed will come up into the froth bed, while if the same seed be introduced below the froth level, only twentyfive to fifty percent of the pure and fertile seed will float. On the contrary, when Indica clover is fed through a froth of the type above noted, none of the clover will float. Even when the seed is fed through the froth-bed, thorough agitation of the machine contents must be had to bring all of the seed material into and through the liquid so that all of the seed material shall be at some time completely immersed in the liquid charge. Only by thorough agitation and recirculation of the seed material through the liquid charge of the. machine can a clean separation be had. Undue retention of the seed in the liquid charge is apt to change characteristics of the seed, and in general the more quickly. the separation is made the better is the result, there being a thorough immersion for a brief period. However, in some cases a longer immersion than is generally employed may be desirable. An example of this is a mixture of wild morning glory seed (Convolvulus arvensis) and Sudan grass seed, which lat-v ter does not lose its smooth glossy appearance after prolonged immersion. In such separation the grass seed comes away as a froth concentrate while the morning glory seed remains as tails.

Generally, reagents such as the lower alcohols do not function as well, alone, as do those that are more persistent in respect to evaporation,

such as pine oil, terpineol, and the like. To strengthen certain bubble walls and give them a. protective armor, such substances as finely ground sulphur, lime-stone, lime, and the like, may be added in small amounts, the addition of such substances frequently being of additional benefit in destroying fungus growth and similar infection carried by the seeds.

As in the flotative separation of minerals, the pH value of the water in the flotation machine is a factor which must be given consideration and regulation in the manner and for the purpose now well understood in the art of froth flotation. In fact, any of the controlling factors entering into minerals separation by froth flotation may be of corresponding value and use in the froth flota tive separation of seeds.

The flnal phase of the improved process involves separate removal of the concentrates, middlings, and tails from the froth flotation machine and ultimate recovery of the seed comprising such separate portions. The froth carrying the concentrates may be caused to overflowaway from the flotation machine, as is common practice in minerals separation, or the froth bed may be skimmed, lifted, or otherwise separated with its seed burden "from the liquid charge within the flotation machine. 1

In some instances it is possible to effect a separation between, seeds of different varieties and simultaneously obtain a selective separation as to relative seed strength of one of the varieties through application of the improved process. As an example, a mixture of blue grass seed and devil grass seed was treated by the improved process using pine oil and the Du Pont frothers B -23" and 3-24 as alternative reagents. the presence of the reagents. noted, the dead and unfertile seeds of blue grass and the live seeds of devil grass collect as concentrates in the froth while the fertile blue grass seeds are left as tails in the machine, so that with a single frothing reagent a'simultaneous separation of the mixture can be made with recovery of the fertile blue grass seeds freed from the unfertile and undesirprovide a froth bed of an inch or more in depth and the machine then'actuated to provide a' circulation and recirculation of the seeds in the presence of the suitable reagents. Only those seeds that actually came up into the froth were removed as concentrates and the balance were considered tails.

After separation was completed, the excess water was drained from the separated seed portions through a one hundred mesh screen, additional water removed through use of a suc-' tion filter, and the seed' then finally dried over a low heat. The separated portions were then weighed for total and relative weights, a certain number of seeds or a certain volume from each seed portion was then planted together with a corresponding number or volume of the unseparated seed, and a careful comparative checkwas made.

1Lettuce seed--100 grams of the seed was first stirred in water for two minutes, one pound of terpineol per ton of seed then added and the miggconditioned for one minute. The separation resulted in grams of concentrates and 15 grams of tails. 100 seeds from both concentrates and tails were then planted and the following rowth observed: In four days: concentrates, 61 sprouts; tails, 7 sprouts. In eighteen days: concentrates, 86 sprouts, all strong plants; tails, 9 sprouts, two strong plants. 2White Clover-100 grams of the seed was thoroughly wetted by stirring in water for two minutes and then was added, per ton of seed, one pound of oleic acid, two pounds of pine oil, and

one pound of DuePont frother 3 23, the said reagents and seed beingconditioned for two minutes. of tails were recovered, 25 cc. of the concentrates weighing 19.6 grams as against a weight of 19.2 grams for a corresponding amount of tails. The concentrates were light colored seeds while the tails were dark in color. 100 seeds from the crude material, the concentrates and tails were then planted with the following results: In four days: crude, 25 sprouts; concentrates, 39 sprouts; tails, 9 sprouts. In eight days: crude, 70 sprouts, concentrates, 96 sprouts, tails 74 sprouts. In thirteen days: crude, 71 sprouts (51 over ,6"), concentrates, 100 sprouts ("I6 over tails, 75

sprouts (66' over ,5"). The leaves of the concentrate seedlings were much flner than those of the tails seedlings.

3-Blue grass-100 grams of the seed was stirred in water for flve minutes and then conditioned for twominutes with Du Pont frother B 24" in the amount of two pounds per ton of seed. The separation produced 36.3 grams of concentratesof which 25 cc. weighed 5.1 grams and 83.4 grams of tails of which 25 cc. weighed 7.8 grams,

After separation was completed 53.2,, grams the concentrates being much lighter in color than the tails.

5 cc. each of concentrates, tails and crude seed was planted in a flat. The growth of the concentrate was only about 5% as good as the growth of the tails at the end of twelve days. The crude seed grew better for the flrst five days but at the "end of twelve days the tails were 50% stronger than the crude.

106 seeds each of concentrates, tails and crude were planted on blotting paper with the following results: In five days: crude; 9 sprouts: con-.

centrates, 1 sprout; tails, 12 sprouts. In twelve days: crude, 76 sprouts; concentrates, 4 sprouts; tails, 94 sprouts.

,which 25 cc. weighed 18.3 grams, the concentrates being much lighter in color than the tails.

100 seeds each from the concentrates and tails were planted with the following results: In two days: concentrates, 55 sprouts; tails, 72 sprouts. In eight days: concentrates, 96 sprouts sprouts over $5"); tails, 90 sprouts (85 sprouts over is").

5-Sugar beetsgrams of the seed was stirred in water for two minutes and then conditioned for two minutes with two pounds per ton of seed of Du Pont frother 3-23. The separation resulted in 88.7 grams of concentrates of which 25 cc. weighed 6.0 grams and 11.3 grams of tails of which 25 cc. weighed 7.2 grams. The seeds in the'tails were all small while the concentrates carried both large and small seeds.

' 42 seeds each from the concentrates and tails were planted with the following results: In three days: concentrates, 3 sprouts; tails, 1 sprout. In nine days: concentrates, 42 sprouts (all over 3" high); tails, 41'sprouts (23 are 2" high). the exception of seven, all of the sprouts from the tails were poor, weak plants with weak stems.

6Oatsl00 grams of the seed was stirred in water for two minutes and then conditioned for one minute with 1.5 pounds DuPont frother and one pound terpineol per'ton of seed. All-of the seed with the exception. of 19 oat seeds and the weed seeds floated, there being no weed seeds in the concentrates. The concentrates and tails were planted on blotting paper. and from 100 seeds of the concentrates 99 sprouts appeared in six days. On the cat seeds in the tails only few sproutwas added and the mixture was then agitated with air until a froth one-fourth of an inch thick was formed. .100 grams of a mixture of alfalfa and Dodder. (Cuscuta) seeds was'then fed to the ,machine through the froth bed and agitated in the machine. 90.6 grams of 'the seeds floated as a concentrate and the tails weighed 9.si grams.

With I Crude. 5 grams; by count there were eleven Dodder seeds. Concentrates, 5 grams; by count.

count there were '51 Dodder seeds. The above -shows that the tails comprising less than ten the improved process in adapting the process for use on and with seeds of differing varieties, I wish to be understood as being limited solely by the scope of the appended claims rather than by any specific details and recitation of the foregoing description.

I claim as my invention- 1. A process for the classification and selective separation of plant seeds which comprises immersion of the seeds in water, addition of a flota-v tive frothing reagent, addition to the mixture of seed and reagent of pulverized insoluble minerals as a strengthening armor for froth bubbles, and subsequent agitation of the resultant admixture in froth-held fiotation apparatus for the separation of the seed material into froth concentrates and non-floating tails.

2. The method of utilizing natural differences in the. surface characteristics of seeds to separate relatively more fertile seeds in a given variety from relatively less fertile seeds of the same variety, which consists of subjecting the seed to violent agitation in froth flotation apparatus in the presence of a reagent consisting of a relatively minute amount of a true frother, for elevation of the seed having one relative fertility characteristic as a concentrate held in the froth bed and separation therefrom of the seed having the other relative fertility characteristic as a tailings product.

3. The method of utilizing natural diflerences in the surface characteristics of seeds to separate the relatively more fertile seed of a given variety from the relatively less fertile seed 'of said variety and from a second variety of seed intermixed therewith, which consists of first subjecting the intermixed seed to violent agitation in froth flotation apparatus in the presence of a reagent consisting of a relatively minute amount of a true frother, for elevation of one seed variety as a concentrate held in the froth bed and separation therefrom of the other variety as a tailings product, recovering the desired seed variety, and subsequently subjecting the recovered seed to violent agitation in froth flotation apparatus in the presence of a reagent consisting of a relatively minute amount of a true frother, for elevation of the seed having one relative fertility characteristic as a concentrate held in the froth bed and separation therefrom of the seed having the other relative fertility, characteristic as a tailings product.

4. The method of utilizing natural differences in the surface characteristics of seeds to separate one variety of seed from a second variety intermixed therewith, which consists of feeding the intermixed seed to froth flotation apparatus through a froth bed formed in said apparatus by the use of a reagent consisting of a relatively minute amount of a true frother, and subjecting said seed to violent agitation in the apparatus in the presence of said reagent for elevation of one seed variety as a concentrate held in the froth bed and separation therefrom of the other variety as a tailings product.

5. The method of utilizing natural differences in the surface characteristics of seeds to separate one variety of seed from a second variety intermixed therewith, which consists of feeding the intermixed seed to froth flotation apparatus through a froth bed formed in said apparatus through the use of a reagent consisting of a relatively minute amount of a true frother and subjecting said seed to violent agitation in said apparatus in the presence of said reagent and a relatively minute amount of a collecting reagent, for elevation of one seed variety as a concentrate held in the froth bed and separation therefrom of the other variety as a tailings product. 6. The method of utilizingnatural differences in the surface characteristics of seeds to separate relatively more fertile seed of a given variety from relatively less fertile seed of said variety, which consists of feeding the seed to froth flotation apparatus through a forth bed formed in said apparatus by the use of a reagent consisting of a relatively minute amount of a true frother, and subjecting said "seed to violent agitation in said apparatus, for elevation of the seed having one relative fertility characteristic/as a concentrate held in the froth bed and separation therefrom of the seed having the other relative fertility characteristic as a tailings product.

7. The method of utilizing natural diiferences in the surface characteristics of seeds to separate relatively more fertile seed of a given variety from relatively less fertile seed of said variety, which consists of feeding the seed to froth flotation ap' paratus through a froth bed formed in said apparatus by the use of a reagent consisting of a relatively minute amount of a true frother, and

- subjecting said seed to violent agitation in said apparatus in the presence of said reagent and a relatively minute amount of a collecting reagent, for elevation of the seed having one relative fertility characteristic as a concentrate held in the froth bedand separation therefrom of the seed having the other relative fertility characteristic as a tailings product, a

8. The method of utilizing natural differences in the surface characteristics of seeds to separate relatively more fertile .seed of a given variety from relatively less fertile seed of said variety and from a second variety of seed intermixed therewith, which consists of first subjecting the intermixed seed to violent agitation in froth fiotation apparatus in the presence of a reagent consisting of a relatively minute amount of atrue frother, for elevation of one seed variety as a concentrate held in the froth bed and separation therefrom of the other variety as a tailings product, recovering the desired seed variety, feeding the recovered seed to froth flotation apparatus through a froth bed formed in said apparatus through the use of a reagent consisting of a relatively minute amount of a true frother, and subjecting said seed to violent agitation in said apparatus in the presence of said reagent, for elevation of the seed having one relative fertility characteristic as a concentrate held in the froth bed and separation therefrom oLthe seed having the other relative fertility characteristic as a 'tailings product. I

9. The method of utilizing natural differences in the surface characteristics of seeds to separate relatively more fertile seed of a given variety from relatively less fertile seed of said variety and from a second variety of seed intermixed therewith, than am of em mustang the intermixed seed-to violent "agitation in froth flotation apparatus in the presence of a reagent consisting of a relatively minute amount of a true frother for elevation of one seed variety as a concentrate held in the froth bed and separation therefrom of the other variety as a tailings product, recovering the desired seed variety,

feeding the recovered seed to froth flotation apparatus through a froth bed formed in said apparatus through the use of a reagent consisting of a relatively minute amount of a true frother, and subjecting said, seed to violent agitation in said apparatus in the presence of said reagent 1 and a relatively minute amount of a collector,

for elevation of the seed-having one relative fertility characteristic as a concentrate held in the froth bed and separation therefromof the seed having the other relative fertility characteristic as a tailings product.

10. The method of utilizing natural differences in the surface characteristics of seeds to separate relatively more fertile seed of a given variety from relatively less fertile seed of said variety and from i a second seed variety intermixed therewith, which consists of feeding the intermixed seed to froth flotation apparatus through a froth bed formed in said apparatus by the use of a reagent consisting of a relatively minute amount of atrue frother, subjecting said seed to violent agitation in said apparatus in the presence of said reagent, for elevation of one seed variety as a concentrate held in the froth bed and separation therefrom of the other variety as a tailings product, recovering the desired seed variety, feeding the recovered seed 3 to froth flotation apparatus through a froth bed formed in said apparatus through the use of a reagent consisting of a relatively minute amount of a true frother, and subjecting said seed to violent agitation in said apparatus in the presence of said reagent, for elevation of the seed having one relative fertility characteristic as a concentrate held in the froth bed and separation therefrom of the seed having the other relative fertility characteristic as a tailings product.

11. The method of utilizing natural differences in the surface characteristics of seeds to separate relatively more fertile seed of a given variety from relatively less fertile seed of said variety and from a second seed variety intermixed therewith, which consists of feeding the intermixed seed to froth flotation apparatus through a froth bed formed in said apparatus by the use of a reagent consisting of a relatively minute amount-of a true frother, subjecting said seed to violent agitation in-said apparatus in the presence of said reagent and a relatively minute amount of a collector, for elevation of one seed variety as a concentrate held in the froth bed and separation therefrom of the other variety as a tailings product, recovering the desired seed variety, feeding the recovered seed to froth flotation apparatus through a froth bed formed in said apparatus through the use of a reagent consisting of a relatively minute amount of a true frother, and subjecting said seed to violent agitation in said apparatus in the presence of said reagent, for elevation of seed having one relative fertility characteristic as a concentrate held in the froth bed and separation therefrom of the seed having the other relative fertility characteristic as a tailings product.

12. The method of utilizing natural differences in the surface characteristics of seed to separate relatively more fertile seed of agiven variety from relatively less fertile seed of said variety and from a second seed variety intermixed therewith,

which consists of feeding the intermixed seed to froth flotation apparatus through a froth bed formed in said apparatus by the use of a reagent consisting of a relatively minute amount of a true frother, subjecting said seed to violent agitation in said apparatus in the presence of said reagent and a relatively minute amount of a collector, for elevation of one seed variety as a con-- centrate held in the froth bed and separation therefrom of the other variety as a tailings product, recovering the desired seed variety, feeding the recovered seed to -froth' flotation apparatus through a froth bed formed in said apparatus through the use of a reagent consistingof a relatively minute amount of a true frother, and subjecting said seed to violent agitation in said apparatus in the presence of said reagent and a relatively minute amount of a collector, for elevation of the seed having one relative fertility characteristic as a concentrate held in the froth bed and separation therefrom of the seed having the other relative fertility characteristic as a tailings product.

13. The method of utilizing naturally differences in the surface characteristics of seeds to I separate relatively more fertile seed of a given variety from relatively less fertile seed of said variety and from a second seed variety intermixed therewith, which consists of feeding the intermixed seed to froth flotation apparatus through a froth bed formed in said apparatus by the use of a reagent consisting of a relatively minute amount of a true frother, subjecting said seed to violent agitation in said apparatus in the presence of said reagent and a relatively minute amount of a collector, for elevation of one seed variety as a concentrate held in the froth bed and separation therefrom of the other variety as a tailings product, recovering the desired seed variety, feeding the recovered seed to froth flotae tion apparatus through a froth bed formed in said apparatus through the use of a reagent consisting of a relatively minute amount of a true frother, and subjecting said seed to violent agi tation in said apparatus-in the presence of said reagent and a relatively minute amount of a collector, for elevation of the seed having one relative fertility characteristic as a concentrate of a true frother, for elevation of the seed of said first variety having one relative fertility characteristic as a concentrate held in the froth bed and separation therefrom of the seed of said first variety having the other relative fertility characteristic as a tailings product, and for separation of the seed of said second variety, as a part of one of said products, from thei'elatively more fertile seed of said first variety.

15. The method of utilizing natural differences in the surface characteristics of seeds to separate the relatively more fertile seed of a first variety from the relatively less fertfle seed of said variety and from a second variety of intermixed therewith, which consists of subjecting the intermixed seed to violent agitation in froth flotation apparatus in the presence of a reagent consisting of a relatively minute amount of a true frother, and in the presence of a relatively minute amount of a collecting reagent, for elevation of the seed of said first variety having one relative fertility characteristic as a concentrate held in the froth bed and separation therefrom of the seed of said first variety having the other relative fertility characteristic as a tailings product, and for separation of the seed of said second variety, as a part of one of said products, from the relatively more fertile seed of said first variety.

16. The method of utilizing natural differences in the surface characteristics of seeds to separate the relatively more fertile seed of a first variety from the relatively less fertile seed of said variety and from a second 'variety of seed intermixed 20 therewith, which consists of feeding the intermixed seed to froth flotation apparatus through a froth bed formed in said apparatus through the use of a reagent consisting of a relatively minute amount of a true frother and subjecting said seed 25 to violent agitation in said apparatus in the presence of said reagent, for elevation of the seed of said first variety having one relative fertility characteristic as a concentrate held in the froth bed and separation therefrom of the the relatively more fertile seed of a first variety from the relatively less fertile seed of said variety and from a second variety of seed intermixed therewith, which consists of feeding the intermixed seed to froth flotation apparatus through a froth bed formed in said apparatus through the use of a reagent consisting of a relatively minute amount of a true frother and subjecting said seed to violent agitation in said apparatus in the presence of said reagent, and in the presence of a relatively minute amount of a collecting reagent, for elevation of the seed of said first variety having one relative fertility characteristic as a concentrate held in the froth bed and separation therefrom off the seed of said first variety having the other relative fertility characteristic as a tallings product, and for separation of the seed of said second variety, as a part of one of said products, from the relatively more fertile seed of said first variety.

THEODORE EARLE. 

